api to access .hi files

[Artem Pelenitsyn]

Hey Sam,

Starting from the implementation of :browse and going through the call
graph in:
https://gitlab.haskell.org/ghc/ghc/blob/master/ghc/GHCi/UI.hs
gave the following, which works for me:

module Main where

import           Control.Monad
import           Control.Monad.IO.Class

import           BasicTypes
import           DynFlags
import           GHC
import           GHC.Paths              (libdir)
import           Maybes
import           Panic

main = runGhc (Just libdir) $ do
  dflags <- getSessionDynFlags
  void $ setSessionDynFlags $ dflags {
      hscTarget = HscInterpreted
    , ghcLink   = LinkInMemory
    }
  t <- guessTarget "Main.hs" Nothing
  setTargets [t]
  _ <- load LoadAllTargets

  graph <- getModuleGraph
  mss <- filterM (isLoaded . ms_mod_name) (mgModSummaries graph)
  let m = ms_mod ms
      ms = head mss
  liftIO . putStrLn $ (show . length $ mss) ++ " modules loaded"
  mi <- getModuleInfo m
  let mod_info = fromJust mi
  dflags <- getDynFlags
  let names = GHC.modInfoTopLevelScope mod_info `orElse` []

  liftIO $ putStrLn $ "seen " <> (show $ length names) <> " Names"

--
Best, Artem

On Fri, 2 Aug 2019 at 15:47, Sam Halliday <sam.halliday at gmail.com> wrote:

> To answer my own question with a solution and another question:
>
> Sam Halliday writes:
> > I'm mostly interested in gathering information about symbols and their
> > type signatures. As a first exercise: given a module+import section
> > for a haskell source file, I want to find out which symbols (and their
> > types) are available. Like :browse in ghci, but programmatically.
>
> This is answered by Stephen Diehl's blog post on the ghc api! How lucky
> I am: http://www.stephendiehl.com/posts/ghc_01.html
>
> He points to getNamesInScope
>
> Unfortunately I'm getting zero Names back when loading a file that
> imports several modules from ghc. Is there something I'm missing in the
> following?
>
> module Main where
>
> import           Control.Monad
> import           Control.Monad.IO.Class
> import           GHC
> import           GHC.Paths              (libdir)
>
> main = runGhc (Just libdir) $ do
>   dflags <- getSessionDynFlags
>   void $ setSessionDynFlags $ dflags {
>       hscTarget = HscInterpreted
>     , ghcLink   = LinkInMemory
>     }
>   addTarget $ Target (TargetFile "exe/Main.hs" Nothing) False Nothing
>   res <- load LoadAllTargets
>   liftIO $ putStrLn $ showPpr dflags res
>   names <- getNamesInScope
>   liftIO $ putStrLn $ "seen " <> (show $ length names) <> " Names"
>
>
> --
> Best regards,
> Sam
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>
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